Two seconds is the time it takes in Formula 1 for mechanics to lift a car, change four tires, and put the car back in movement. It is difficult to believe that you cannot swap flop drives in less than that time.
Those usually had a lever rather than a button so it was a 4 step process rather than a 3 step process:
3.5":
- Press button
- Remove Disk
- Insert Disk
5.25"
- Turn lever
- Remove Disk
- Insert Disk
- Turn lever
Add to this the fact that 5.25" floppies were less rigid, and expensive enough that you don't want to damage, and it takes a lot longer.
That being said, I think I did get down to just barely under 2s when I was restoring my hard disk from 97 5.25" floppies after getting a virus (the backup program being used bypassed DOS's system calls for accessing the disk, and polled multiple times per second so you didn't even need to press a key after inserting the disk).